The invention relates to a diamond cutting tool with a synthetic diamond layer having a cutting edge, and a process for producing a diamond cutting tool.
Diamond is a suitable material for cutting tools due to its excellent mechanical, chemical, thermal and electrical properties. A diamond cutting tool having a substrate and a cutting edge element based on diamond arranged on the substrate is known from European application 0 577 066. The cutting edge element may comprise a diamond layer deposited from the vapour phase. The cutting edge element is structured with the aid of a laser beam and then attached to the substrate material. The disadvantages of this cutting tool are the high production costs due to the expensive laser structuring of the cutting edge and the attachment of the cutting edge element to the substrate material which is not simple in terms of process engineering. It is also disadvantageous that the cutting edge angle cannot be set to be as small as required.
In the introduction of European application 0 577 066, a diamond cutting tool made from a substrate material which is coated with diamond is described as state of the art. However, the disadvantage of this diamond cutting tool is that the thin film of diamond is separated from the substrate material during cutting.
Starting from the disadvantages of the state of the art, the object of the invention is to indicate a diamond cutting tool which can be produced in simple manner in large numbers and cost-effectively, has considerable sharpness and mechanical stability and may be provided with any shape cutting surfaces. The object of the invention is also to indicate a process for producing such a diamond cutting tool.
This object is achieved by a cutting tool according to claim 1 and a process for producing a cutting tool according to claim 12. The particular sub-claims relate to preferred embodiments and further developments of the invention.
A diamond cutting tool can be produced in simple manner and has a cutting edge of considerable sharpness if the cutting edge of the synthetic diamond layer has a profile of decreasing layer thickness which is structured by etching. During production of this diamond cutting tool, after depositing the diamond layer on a preferably crystalline substrate material, the cutting edge is formed by carrying out one or more etching steps. During etching, an etching mask is used which is etched separately from the diamond layer or at the same time as the diamond layer. The optionally structured substrate material and/or one or more optionally structured further layers, which have been applied to the diamond layer, may act as etching mask. The angle of the cutting edge can be set specifically by varying the ratio of the etching rates of etching mask and diamond layer.
Cost-effective production, which can be automated, of the diamond cutting tool according to the invention is guaranteed in high numbers, if the diamond layer is initially deposited on a large surface area support material, and before carrying out the at least one etching step to produce the cutting edge, structuring of the etching mask is carried out to define individual cutting tools of any geometry.
The diamond layer is preferably textured and particularly preferably has a  less than 111 greater than , or  less than 110 greater than  or  less than 100 greater than  texture. A texture is meant when more than 80% of the surface of the diamond layer is formed by  less than 111 greater than , or  less than 110 greater than  or  less than 100 greater than  diamond surfaces, and the difference of the Euler angle xcex94xcex3 between the  less than 111 greater than ,  less than 110 greater than  or  less than 100 greater than  diamond surfaces lying against one another and defining the orientation of the diamond layer, fulfils the condition |xcex94xcex3|xe2x89xa620xc2x0. The thickness of the diamond layer is preferably between 1 and 500 xcexcm and the average surface roughness RA preferably less than 5 xcexcm. Following the deposition of the diamond layer, the latter may be further processed mechanically, physically or chemically to reduce optionally existing surface roughness of the diamond layer.
The diamond layer may be deposited on preferably etchable substrate materials, such as silicon, silicon carbide, glass, refractory metals, sapphire, magnesium oxide or germanium. It has been shown that the diamond film still lies on a substrate (1 monolayer 20 nm SiC) after removing the Si layer and is not co-removed during removal.
The cutting edge of the diamond cutting tool is preferably defined by a dry-chemical etching step, such as for example reactive ion etching. Etching mask and diamond layer may be etched at the same time in a single etching step. Alternatively, it is possible to etch etching mask and diamond layer separately in two or more etching steps. If more than two etching steps are carried out, a graded profile may be formed in the diamond layer. By varying the ratios of the reactive glass components during etching it is possible to exert influence on the shape of the cutting edge. For example, arched cutting edges can be realised in this manner. The profile of the etching process may also be defined as stepped/graded profile, which has as minimum step height the lattice constant of the diamond (a=3.5 xc3x85).